This invention relates to a vascular prosthesis with an elastomer coating that is mechanically strong, flexible, and substantially nonporous, and does not require preclotting prior to its implantation.
Vascular prostheses are used as substitutes for portions of blood vessels when portions of blood vessels in a patient must be removed or bypassed because of clotting or disease. Such prostheses can be made of synthetic materials, especially of woven or knit polyester tubing. This type of tubing is preferred to solid, extruded tubing because it is not as rigid or subject to kinking and, therefore, can be formed into a variety of shapes without difficulty and without unduly restricting the blood flow. Such porous tubing normally is soaked in the patient's blood, and the blood is allowed to clot prior to use. This makes the tubing nonporous and, in addition, it facilitates the growth of endothelial cells on the blood-coated surfaces. As an alternative, the woven or knit tubing is coated either on the inner or on the outer surface, or on both surfaces with a polymeric material, which makes the tubing nonporous. Some polymeric coatings also support endothelial cell growth. Such coated tubing eliminates the need for presoaking in patient's blood and preclotting.
Various methods of applying polymeric materials to porous tubing to form either porous or nonporous coatings for the purpose of making vascular prostheses are known. For example, U.S. Pat. No. 4,304,010 (to Mano) describes a porous poly(tetrafluoroethylene) vascular prosthesis tubing coated on the outside with elastomer materials, especially with fluorine rubbers. Coating can be applied from a solution also containing a blowing agent, or from a solution in a mixture of a solvent and a nonsolvent and drying to form a porous coating, or coating an elastomer solution on the outside of the tubing and removing the solvent by dipping the coated tubing in a nonsolvent bath and heating above the boiling point of the solvent to render the coating porous. U.S. Pat. No. 4,632,842 (to Karwoski et al.) describes a process for applying a fluorine-containing coating to a porous tubular substrate by means of a glow discharge. U.S. Pat. No. 4,656,083 (to Hoffman et al.) describes a process for treating articles to improve their biocompatibility by exposing a substrate material to plasma gas discharge in an inert gas atmosphere and then in the presence of an organic gas such as, for example, a halohydrocarbon.
As can be seen, the above processes either produce a porous coating, which is not intended here, or require rather complicated techniques and apparatus. It is, therefore, desirable to provide a substantially nonporous vascular prosthesis of a simple design, which can be made by a convenient and inexpensive process not requiring complicated special equipment.